Smart watches and wearable devices are gaining more and more popularity, with over 450 million sold worldwide and an annual predicted growth of 20%. These devices have now created a new trend – wearable devices capable of estimating heart rate. Due to the increasing availability and popularity of this technology, the number of patients seeking medical advice due to abnormalities detected by the wearable devices is increasing.
Towards the end of 2018, technology giants Apple announced that the Apple Watch Series 4 would have capability of recording an electrocardiogram (ECG) right from users’ wrists. They have worked with the Food and Drug Administration (FDA) for years to gain De Novo classification of their ECG app and notification feature, allowing them to make them available over the counter. Impressively, the new smart watch was announced to come with an irregular rhythm notification feature, which occasionally checks heart rhythms in the background and notifies users if an irregular heart rhythm that appears to be in atrial fibrillation is identified.
Wrist-worn smart watches, like Apple’s, calculate heart rate by photoplethysmography (PPG), which use an infrared light-emitting diode and photodetector to monitor blood volume changes in the microvasculature. Among scientists, this method has been questioned; in healthy control patients, tests have displayed variable accuracy depending on factors such as the device used and activity undertaken. A recent study in Australia tested the accuracy of both the Apple Watch and FitBit for heart rate estimation in hospitalised patients with atrial arrhythmias, rather than healthy, normal patients. They found that both devices demonstrated strong agreement with results from continuous ECG monitoring during normal heart rhythm, and, interestingly, results were consistent during atrial flutter. However, while they were generally in agreement, there was a small tendency for the devices to underestimate heart rate in atrial fibrillation.
So, whilst there may have previously been some doubts, recent studies seem to be suggesting that devices such as the Apple Watch Series 4 are becoming more accurate. And whilst there is definitely still room for more clinical and academic studies on these devices, it is a positive sign that users are getting themselves checked by medical professionals as a result of these devices’ warnings. Atrial fibrillation is the most common form of irregular rhythm, and when left untreated it is a leading cause of stroke. Therefore, these devices are an innovative and useful product, that have potential to change the world of cardiology. Still, users should remain aware of possible inaccuracies.
Annie Hill, Healthcare21 Communications, Macclesfield
- Apple. 6 December 2018. https://www.apple.com/newsroom/2018/12/ecg-app-and-irregular-heart-rhythm-notification-available-today-on-apple-watch/ [Last accessed March 2019].
- Apple. Apple Support. https://support.apple.com/en-gb/HT208955 [Last accessed March 2019].
- Koshy A, Sajeev J, Nerlekar N, et al. Smart watches for heart rate assessment in atrial arrhythmias. International Journal of Cardiology. 2018;266:124–7.